I have always been of the opinion that there is a difference between tripping, and being tripped.
That said, what if a player is in legal guarding position, and has their feet wider than their shoulders, and, for sake of argument, has obtained that position on the court, and remains in that position for, let's say, oh, ten seconds, motionless, and then a dribbler tries to dribble past this motionless defender and trips over the defender's leg. I have a no call. Please correct me if I'm wrong. Please.